It is insane. I can shape shift into something with a dex of 24 and STILL not hit the damn thing with a ranged touch attack. I may just re-roll her and drop the 3 levels of HFW just to get the Cone shape. Maybe with my high CHA I'll get through the SR. Its sad, because I just loved the idea of this character.

Can you saturate the battlefield w/ Chill Tent & Wall of Perilux Flame before ole Blue becomes hostile? I recall those working on very high SR races. Extend Spell metamagic is supposed to work on Invokes IIRC. Double duration = double dam.

I was wrong about Extend Spell working on Invokes & Spells. It doesn't. The feat that works on both was Spell Pen.

Just to help out, no, metamagic feats do not work with invocations (because invocations are not 'spells', they're 'spell-like abilities' ). Spell Penetration works for both invocations and your eldritch blast ..."

Spamming summons is one of them - plague of undead is kinda powerful, the dead walk might provide unlimited meat. As for SR, it is a pain in the ass especially if you lost warlock levels. Abandoning hellfire warlock, however, won't help with that - hellfire warlock advances invoker level as it should. delaying hellfire warlock until higher levels would only gain you 1 BAB. Abandoning shifter would also gain 1 BAB, but lose you the dex you get from the shape.

Hellfire shield delivers eldritch blast damage and requires a reflex save, so it would hit, no idea about the SR though.

As far as Wall of Perilous Flame goes, it is bugged in that it deals (2d6+1)*Invoker Level damage instead of 2d6 +1*Invoker level. It still shouldn't penetrate SR automatically, but since you can stack that there's a high chance it will hit eventually. Then you can just Flee the Scene to the other side of the flames.

Lost Boy - eldritch chain on a lackey won't work as every creature struck requires a separate touch attack.

Overall practiced invoker is your friend, Since you need to be level 9 to get hellfire warlock and you were hfw 3, I guess you were level 12. With practiced invoker you would get one greater invocation leaving you with 3 least, 1 lesser, 1 greater. If you chose to pick warlock at level 9 you could get another least invocation through extra invocation. You could also get weapon focus ray for another +1 to attack - no idea if that would help though as I don't know the AC of the blue dragon - is it an adult blue dragon? If yes, his AC should be 28 - no idea about the touch AC though.

What to do with those: I like the trick with darkness+devil's sight, but I think dragons true seeing nullifies that. Summon swarm? Probably will not punch through DR. Beguiling influence helps avoid fights, while dark one's own luck helps with what Lost Boy said. Lesser invocations have chain, baneblast adds damage, but doesnt help punch through SR or hit, so pass. And you can't hit him with eldritch chain anyway... I dont think anything here helps you that much except flee the scene for running and ignore the pyre for elemental damage resistance. Oh, and the dead walk to make a meat shield.

Greater invocations is where its at: wall of perilous flame won't punch through SR but thanks to a bug deals immense damage. Stackable. Eldritch cone and line let you target reflex save with your EB, but won't punch through SR. Vitriolic blast is amazing, but you have to hit the touch attack. I believe the best option is to get chilling tentacles and stack the hell out of them. They ignore SR, deal bludgeon damage, on failed save root the dragon in place (won't happen often - but you STACK the tentacles) and deal 2d6 cold each round - I don't think there's a save on this. Just spam it and run in circles. Flee the scene and ignore the pyre should work just fine for that.

TL;DR Get chilling tentacles, with practiced invoker you can get one greater invocation at level 12 and it should be this one.

"Starting at 3rd level, you can call up hellfire to surround yourself with a protective barrier. Whenever someone directs a melee attack against you, [My guess is that the opp has to hit you to trigger, rather than take a swing.If opp's really take HF Shield damage per swing (not per hit), Expertise might not be that bad.] you can, as an immediate action, aim a blast of hellfire at that creature. This blast deals damage equal to your eldritch blast (including bonus damage from the hellfire blast ability). This blast automatically strikes the target, which can attempt a Reflex saving throw for half damage (DC 10 + 1/2 your character level + your Cha modifier) . . . [No need for attack roll, but you'll likely take more damage from a dragon than HF Shield will deal. If Blue has Imp Evasion, it's a dead end.]

. . .Each time you use this ability, you take 1 point of Constitution damage. Because the diabolical forces behind the power of hellfire demand part of your essence in exchange for this granted power, if you do not have a Constitution score or are somehow immune to Constitution damage, you cannot use this ability." [Get a Lesser Resto item going to heal the Con dam.]

+100 this advice before you re-do / toss your whole build: load Chill Tent & Prac Invoker (Chill T will last up to 4 rounds longer each [depends on your shifter level]) and spam the battlefield.

Undead are immune to both L-ning and your Chill T cold. Blue will have to melee pound them. All the while Chill T is doin' its thang.

The UMD check for a True Strike scroll ~ 21. Your build should hit that reliably. Not that you'd want to waste a feat, but UMD skill foc (+3) is an option.

OMFSM I did not realize that you could SPAM the heck out Chill Tents. So yeah, U de-leveled and re-leveled as straight 'lock. Took Dead Walk and Chill Tent. Took Blue down in just a few mins. Now to get rid of Big Red.

You should have went 9 lock/3 hellfire lock. You get the same amount of invocations as a straight lock, only delay your imbue item (if you're going to craft items...).

Lost Boy - according to the description of Evard's Black Tentacles the duration is caster level/2 rounds, so practiced invoker gives up to 2 additional rounds. It matters, but it's still an awesome invocation.